In a liquid crystal display element, a display element using a nematic liquid crystal is now prevailing. Display elements by various systems are put in practical use, for example, a matrix TN element in which a liquid crystal molecule is twisted 90 degrees, a STN element in which a liquid crystal molecule is usually twisted 180 degrees or more, a TFT liquid crystal display element using a thin film transistor, and an IPS (In Plane Switching) mode liquid crystal display element having improved viewing angle properties. The progress of liquid crystal display elements is not limited to only these modes, but active efforts to improve peripheral materials have been made towards the improvement in characteristics of liquid crystal display elements.
A liquid crystal aligning film is one of important elements concerning the display quality of a liquid crystal display element, and its role becomes large as high quality of a display element is required.
Presently, mainly used materials for the liquid crystal aligning film are polyamic acid aligning agents used after imidization of polyamic acid, and soluble polyimide aligning agents. According to prior references, a variety of other high-molecular aligning films have been investigated. However, almost of them have not been put in practical use in light of heat resistance, chemical (liquid crystal) resistance, coating properties, electrical properties, display performance, alignment stability of liquid crystal molecule, etc.
In addition to polyimides, polyamides and other polyamides wherein H in an amide group (CONH) is substituted by other group have been investigated, but they have drawbacks in the alignment property, electrical properties of liquid crystal elements, etc. There are aligning agents containing polyamic acids and polyamides, but they have drawbacks in the image sticking, residual charge, voltage holding ratio, etc.
Thus, conventional liquid crystal aligning films have not fulfilled the required properties totally and with good balance.